Image forming apparatus

1. An image forming apparatus, comprising: an image forming unit configured to form an image on a recording medium using a discolorable coloring material which discolors by heating or a non-discolorable coloring material; a heating unit configured to heat the image formed on the recording medium at a fixing temperature lower than a discoloring temperature at which the discolorable coloring material discolors, to fix the image on the recording medium or heat the image formed on the recording medium at the discoloring temperature to discolor the image; a feed cassette configured to house a recording medium for image forming by the image forming unit; a first conveying path configured to convey the recording medium for image forming from the feed cassette to the heating unit through the image forming unit, the first conveying path has a first conveying unit to convey the recording medium for image forming; a feed tray configured to hold a recording medium for image discoloring by the heating unit; a second conveying path configured to join the first conveying path at a position between the image forming unit and the heating unit and convey the recording medium for image discoloring from the feed tray to the heating unit the second conveying path has a second conveying unit to convey the recording medium for image discoloring; a temperature control unit configured to control a heating temperature of the heating unit to the fixing temperature or the discoloring temperature; and a driving unit configured to drive the image forming unit, the heating unit, the first conveying unit and the second conveying unit, wherein the driving unit drives the heating unit and the second conveying unit and stops driving of the image forming unit and the first conveying unit, in a case that the heating unit heats the image formed on the recording medium to discolor the image.

2. The image forming apparatus according to claim 1 , wherein the driving unit has a first motor to drive the image forming unit, a second motor to drive the first conveying unit and the second conveying unit, a third motor to drive the heating unit independently from the image forming unit, the first conveying unit and the second conveying unit and a motor driver to control the first motor, the second motor and the third motor.

3. The image forming apparatus according to claim 2 , wherein the motor driver controls the first motor, the second motor and the third motor so that only the heating unit and the second conveying unit are driven, in a case that the heating unit heats the image formed on the recording medium to discolor the image.

4. The image forming apparatus according to claim 1 , further comprising a first sensor configured to detect the heating temperature of the heating unit.

5. The image forming apparatus according to claim 4 , wherein the temperature control unit controls the heating temperature of the heating unit based on the detection result of the first sensor.

6. The image forming apparatus according to claim 5 , wherein the heating unit heats the image formed on the recording medium to discolor the image in a case that the first sensor detects that the heating temperature of the heating unit reaches the discoloring temperature.

7. The image forming apparatus according to claim 6 , further comprising a second sensor configured to detect presence or absence of the recording medium held by the feed tray.

8. The image forming apparatus according to claim 7 , wherein the heating unit heats the image formed on the recording medium to discolor the image in a case that the first sensor detects that the heating temperature of the heating unit reaches the discoloring temperature and the second sensor detects the presence of the recording medium held by the feed tray.

9. An image forming apparatus, comprising: an image forming unit configured to form an image on a recording medium using a discolorable coloring material which discolors by heating or a non-discolorable coloring material; a heating unit configured to heat the image formed on the recording medium at a fixing temperature lower than a discoloring temperature at which the discolorable coloring material discolors, to fix the image on the recording medium or heat the image formed on the recording medium at the discoloring temperature to discolor the image; a feed cassette configured to house a recording medium for image forming by the image forming unit; a first conveying path configured to convey the recording medium for image forming from the feed cassette to the heating unit through the image forming unit; a feed tray configured to hold a recording medium for image discoloring by the heating unit; a second conveying path configured to join the first conveying path and convey the recording medium for image discoloring from the feed tray to the heating unit; a temperature control unit configured to control a heating temperature of the heating unit to the fixing temperature or the discoloring temperature; and a first sensor configured to detect presence or absence of the recording medium held by the feed tray; wherein the heating unit heats the image formed on the recording medium to discolor the image in a case that a second sensor detects that the heating temperature of the heating unit reaches the discoloring temperature and the first sensor detects the presence of the recording medium held by the feed tray.

10. The image forming apparatus according to claim 9 , wherein the second sensor configured to detect the heating temperature of the heating unit.

11. The image forming apparatus according to claim 10 , wherein the temperature control unit controls the heating temperature of the heating unit based on the detection result of the second sensor.

12. The image forming apparatus according to claim 11 , wherein the heating unit heats the image formed on the recording medium to discolor the image in a case that the second sensor detects that the heating temperature of the heating unit reaches the discoloring temperature.